A generally available casing of an electronic device such as a mobile phone or a smartphone is configured by combining a front casing and a rear casing that are made of a synthetic resin. Usually fixed onto a surface of the front casing, by fusion bonding or the like, is a protection panel for protecting a liquid crystal display window.
On the other hand, the electronic device such as the mobile phone or the smartphone is sometimes provided with a touch panel that is mounted on a liquid crystal display screen so as to enable touch input operations to the liquid crystal display screen. In this case, the liquid crystal display window of the casing is left open as there cannot be provided a protection panel that inhibits input operations to the touch panel disposed therebelow.
However, Patent Document 1 has recently disclosed a new protection panel that is obtained by adding a touch input function to the protection panel described above. Specifically, as shown in FIG. 12, a protection panel 100 for a display window of an electronic device includes a protection panel main body 107 configured by a transparent plate, a lower electrode sheet 101 that has a quadrilateral lower transparent electrode 102 placed on an upper surface of a transparent resin film and a lower circuit 105b provided at a periphery of the lower transparent electrode 102, and is attached onto an upper surface of the protection panel main body 107, an upper electrode sheet 103 that has a quadrilateral upper transparent electrode 104 disposed on a lower surface of a transparent resin film and an upper circuit 105a provided at a periphery of the upper transparent electrode 104, and is bonded to the lower electrode sheet 101 at peripheral edges thereof with a gap 120 being formed between the electrodes 102 and 104, a decorative sheet 108 that has on at least one of surfaces of a transparent resin film a decorative layer 109 shaping a transparent window portion 108a so as to hide the lower circuit 105b and the upper circuit 105a, and is attached onto an upper surface of the upper electrode sheet 103, and a flexible printed circuit board (FPC) 118 that has an end inserted between the lower electrode sheet 101 and the upper electrode sheet 103 and is connected by thermal compression bonding to output terminals 123 and 124 of the upper circuit 105a and the lower circuit 105b, respectively (refer to FIGS. 12 and 15). The protection panel 100 for a display window of an electronic device is configured to be fitted and retained with no gap in a panel fitting portion 122 of a casing 113 provided with an opening such that an outer surface of the protection panel 100 forms one plane together with a periphery thereof. The protection panel 100 protects a display device 115 that is disposed therebelow so as to be externally visible through the transparent window portion 108a (refer to FIGS. 13 and 14).
The protection panel 100 for a display window of an electronic device is thus configured to allow touch input operations onto a liquid crystal display screen. Furthermore, there is formed in the protection panel no difference in height among the surface of the transparent window portion 108a, the surface of a decorative portion 111 surrounding the transparent window portion 108a, and an outer surface 121 of the casing 113 (refer to FIG. 14). The transparent window portion 108a thus appears integrally with the casing 113 in view of design thereof.